1. Field of the Invention
The present invention relates to a method for finely granulating granular substances with pollutants such as incinerated ashes adhered.
The present invention relates to a method for carrying out fine granulation of granulating granular substances with pollutants such as soils contaminated by heavy metals, oily constituents and the like adhered and incinerated ashes conveyed from through flying incinerator and also carrying out separation of granular substances without containing pollutants or granular substances, from which most of the pollutants are removed, from the granular substances which are subjected to fine granulation treatment mentioned as above.
2. Description of the Prior Art
Hitherto, unrecycable inflammable substances such as unrecycable raw garbages have been burnt up through a stoker type or fluidized bed type incinerator and the burnt up ashes have been transferred as incinerated ashes to a disposal plant.
In actual incinerated ashes, burnt up scraped metal, fragments of burnt up scraped metals, potteries or earth and sand those of which are burnt up being mixed in the inflammable substances as mentioned above are contained, and consequently in the constituents of incinerated ashes various kinds of metals, silica, alumina and lime are mixed. Since this sort of incinerated ashes are large in scraped volume and are adhered with noxious materials such as heavy metals and dioxin class substances and the like, which are produced during the incineration process, establishment of a technology for method of reduction of volume of the incinerated ashes, rendering the same to be non-noxious or recycling the same.
A method for reducing the noxious heavy metals such as lead, zinc, copper and cadmium to unnoxious following methods are enumerated: (1) solidification through fusion, (2) solidification by cement, (3) treatment by agent, (4) stabilization by acid or other solvent, (5) treatment by carbonation and (6) washing by water. Among those, the surest method is the solidification through fusion of (1) and this method is to scrap the incinerated ashes to a disposal plant or recycle them as extra minute fragments of grains after fusion at a high temperature exceeding 150xc2x0 C. and today this method is put to practical use. In this method, even when the fused substances contact with water, elution of heavy metals mentioned as above is not said to happen because the heavy metals are trapped within the fused substances.
Since in the method 2 of solidification by cement, the cement is mixed in the incinerated ashes, there exists a fatal disadvantage that the volume of the incinerated substances increases. Further, alkaline of the incinerated ashes, which are subjected to mixing cement in them, is intensified and hence risk of elution of lead and the like is rather built up. In the method 3 of treatment by agent, a pH adjustment is important and still, due to the reason that kinds of substances contained in the incinerated ashes are varied and not to be fixed, pH adjustment is not easy and addition of agent is supposed not to be effective when the pH adjustment is not carried out adequately. In the method 4 of stabilization by acid or other solvent, because the stabilization is carried out in a condition with heavy metals remained, it is hard to prevent heavy metals from elution in long term. In the method 5 of treatment by carbonation, maintenance control of the plant is hard and further equipments are complicated and hence this method is not practical. In the method 6 of washing by water, it is supposed that removal of heavy metals are carried out relatively easily if the environment is not acidified by acid rain but the effect of the method is merely assured by flying ashes in the powder state. Consequently, in this method sufficient effect can not be anticipated for the heavy metals and dioxin class substances adhered to granular substances in a massed granular state.
Also the aforementioned method of solidification through fusion allows reducing dioxin class substances to be unnoxious by thermal discomposition by virtue of a high temperature of treatment of the incinerated ashes, in view of the present situation it is said that this method of solidification through fusion is most effectual and hence this method bears main stream among various method.
However, in view of considerations over a long period of time, in the solidification through fusion too, the possibility of elution of heavy metals trapped within the fused substances buried in the disposal plant can not be denied. Further, there gives rise problems such that construction cost of the facilities and treatment cost are high because large facilities such as incinerating furnace and a large quantity of fuel are required for the solidification through fusion due to high temperature for fusing incinerated ashes.
On the other hand, in recent years, there gives rise to a problem such that soils in the vicinity of chemical factories and metal refineries are contaminated by heavy metals, organic chlorine or oily constituents. Also beach shore soils contaminated by crude oil being effluent to ocean because of disasters at sea and also crude oil adheres to the drug out soils which are conveyed through a tunnel digging of a land subsidence at the area of crude oil deposited and consequently the treatment of such soils becomes hard frequently. Further, the soils with pollutants in questions adhered (contaminated soils) include the soils which are contaminated by mixing aforementioned incinerated ashes into them.
As to soils contaminated mentioned as above too, establishment of a technology for removing aforementioned pollutants and for recycling stones, sands and extra minute grains contained in the contaminated soils after extracting them is anticipated.
Generally speaking, it is said that dioxin class substances adhered to the incinerated ashes sticks to relatively strongly to the surfaces of granular substances with diameters below 2 mm in the incinerated ashes. Then, upon classifying granular substances with diameters more than 5 mm from the incinerated ashes, carrying out treatment for removing dioxin class substances adhered relatively weakly to the aforementioned surfaces, those granular substances are supposed to be unnoxious and allowable to be recycled. In spite of such a situation, as far as the inventor of the present invention is concerned, no methods are proposed for separating the incinerated ashes in a state of massed granular substances to individual granular substances without crushing them and also detaching the dioxin class substances from the granular substances below 2 mm to which dioxin class substances is said to stick relatively strongly.
Also since the incinerated ashes are formed of a soft texture, it is not only hard to detach dioxin class substances adhered to them by means of an usual crushing machine but it is not possible to do so because, if the incinerated ashes are crushed by crushing machine, for example a ball mill, the granular substances of the incinerated ashes are also granulated and thus the granular substances with dioxin class substances adhered can not be separated and, on the contrary, reduction of their volume becomes hard.
In the contaminated soils, though the portions where the granular substances mutually constituting soil grains become to a massed granular state are limited, likewise the aforementioned incinerated ashes, not only detachment of pollutants as above by means of an usual crushing machine is hard but also soil grains in the contaminated soils too are reduced to be granulated because the diameters of pollutants such as heavy metals and oily constituents are extremely small; thus separation of those pollutants are hard.
On the other hand, Japanese Laid-Open Patent Application No. 8-164363 discloses a crushing machine 10 for removing acute angle portions of stones and the like in the dredged soils without crushing dredged soils containing sands, gravels and clays and also for crushing the clods of solids, sands and the like. FIGS. 32(a) and (b) show constitution of the crushing machine 10: (a) is a side view and (b) is sectional view cut away along Axe2x80x94A of (a). The crushing machine 10 is provided with a rotary drum 6 having a plurality of outer blades 6W, which are attached along its inner peripheral surface in its axial direction protruding toward its center, and is provided with a rotor 7 being installed within the rotary drum 6 eccentrically with it having a plurality of inner blades which are attached to its outer peripheral surface protruding in radial direction; an annular gear provided on the periphery of the rotary drum 6 is driven by a motor 8 and the rotary shaft 7a attached to the rotor 7 is driven by a driving unit 7b, and by rotating the rotary drum 6 and rotor 7 in a mutually reversed direction, carries out crushing substances such as dredged soils thrown into the crushing machine 10 upon compressive forces and shearing stresses exerted on the substances thrown into and polishing the substances which have been crushed through mutual frictions among the crushed substances themselves. Now the crushing treatment by the crushing machine 10 is carried out in a dried or wet condition at the time of polishing the crushed stones and is carried out while pouring water to the substances poured at the time of rendering the earth and sands such as dredged soils such as sands, gravels and clays to extra minute grains. The magnitude of stress to be exerted on the above substances poured into is adjusted mainly by gap between the rotary drum 6 and the rotor 7 (degree of eccentricity of the rotor 7) and by respective rotation speeds of the rotary drum 6 and rotor 7.
And though the above prior art discloses an example for crashing gravels and stones contained in the dredged soils by the crushing machine 10 yet, means for separating granulated substances being reduced to massed grains such as incinerated ashes obtained by burning up sources of organic substances such as raw-garbages and inflammable substances without destroying the above granular substances or for rendering incinerated ashes to unnoxious by separating heavy metals and dioxin class substances adhering to the granular substances in the incinerated ashes are not suggested at all.
Also, as far as relying on the crushing machine 10, it was hard to effectively detach the pollutants adhering to each of granular substances consisting of soil grains of the above contaminated soils when the substances to be treated are the contaminated soils adhered with pollutants having a large viscosity such as carbon and oily constituents or when the contaminated soils are such that heavy metals, i.e. pollutants, adhere strongly to each of the individual granular substances.
Further, none of the means are suggested for recycling unnoxious substances obtained through separating pollutants from incinerated ashes and contaminated soils.
The present invention has been made in view of the problems in the past, and its object is to provide a method and system for treatment of granular substances with pollutants adhered which enable to carry out fine granulation of the granular substances with pollutants, such as contaminated soils and incinerated ashes, adhered and to carry out separation and removal of the pollutants efficiently and further to carry out recycling the unnoxious granular substances with pollutants separated.
A method of carrying out treatment of granular substances with pollutants adhered according to a first aspect of the present invention including a step of finely granulating the granular substances by a fine granulation means in which the granular substances with pollutants adhered are poured into a treatment gap of the fine granulation means and in which granular substances are separated into independent granular substances and also in which the pollutants adhering to surfaces of the granular substances are separated by having compressive forcers exerted on the granular substances and having mutual rubbing forces acted on the same among themselves while adding water to the poured granular substances with pollutants adhered, and characterized in that fine granulation step, the compressive stress to be exerted on the granular substances are arranged to be gradually increased.
In detail, this invention is characterized in that at first by having the compressive stresses exerted on the granular substances with pollutants adhered, treatment of fine granulation, i.e. separation of the granular substances, which are in the state of massed granular substances being formed by mutual sticking of many granular substances among themselves, with pollutants adhered into almost independent granular substances without destroying them is carried out (hereinafter referred to as disintegrating treatment); and next, by having mainly mutual rubbing forces acted on the finely granulated granular substances upon increasing stresses to be applied to them and causing mutual polishing by mutual frictions among the granular substances and thus the pollutants adhering to granular substances are separated (hereinafter referred to as glue breaking treatment).
A method of carrying out treatment of granular substances with pollutants adhered according to a second aspect of the present invention is characterized in that after carrying out the fine granulation treatment on the granular substances with pollutants adhered by a single fine granulation means, carrying out the fine granulation treatment for the second time by pouring the granulation substances, which were already subjected to the fine granulation treatment, into the same fine granulation means and at the time of second treatment, stress to be applied to granular substances are made larger than the one being applied previously.
A method of carrying out treatment of granular substances with pollutants adhered according to a third aspect of the present invention is characterized in that the treatment is carried out by the fine granulation means which is provided with a cylindrical rotary drum having a plurality of outer blades attached to an inner peripheral surface of the rotary drum toward its center and a rotor having a plurality of inner blades, which are attached to an outer peripheral surface along an axial direction protruding in a radial direction of said rotor, and being installed within the rotary drum eccentrically with the same and having arranged to rotate in a reversed direction of the rotary drum.
A method of carrying out treatment of granular substances with pollutants adhered according to a fourth aspect of the present invention is characterized in that, under a condition that hard substances are mixed in the granular substances with pollutants adhered, the fine granulation treatment is carried out by accelerating the substances by rotating the rotary drum and the rotor in a mutually reversed direction.
A treatment means of granular substances with pollutants adhered according to a fifth aspect of the present invention is provided with a single fine granulation means in which by having compressive forces exerted on the granular substances with pollutants adhered and by having mutual rubbing forces acted on the same among the substances themselves, which have been poured into a treatment gap of the treatment system, while adding water to the granular substances, the granular substances are separated to independent granular substances and also the pollutants adhering to surfaces of the granular substances are separated, wherein the treatment gap of the fine granulation means is set narrow on the downstream side, so that the disintegration and glue breaking treatments of the granular substances with pollutants adhered can be carried out efficiently.
A treatment system of granular substances with pollutants adhered according to a sixth aspect of the present invention is provided with a plurality of fine granulation means over a plurality of stages for separating the granular substances to independent granular substances and separating the pollutants adhering to surfaces of the granular substances, while adding water to the granular substances being poured into a treatment gap, by having compressive forces exerted on the granular substances with pollutants adhered and by having mutual rubbing forces acted on the same among the substances themselves and the granular substances are arranged to pass through successively each of the granulation means and the treatment gaps are set gradually narrower at downstream stages.
A treatment system of granular substances with pollutants adhered according to a seventh aspect of the present invention, wherein a means for carrying out dehydration treatment of a slurry discharged from a prestage fine granulation means is provided and the substances which have been subjected to the dehydration treatment, are poured into the fine granulation means of latter stage.
A fine granulation system for carrying out treatment of granular substances with pollutants adhered according to an eighth aspect of the present invention employs a fine granulation means and the fine granulation means is provided with a cylindrical rotary drum having a plurality of outer blades attached to an inner peripheral surface of the rotary drum toward its center and a rotor having a plurality of inner blades, which are attached to an outer peripheral surface along an axial direction protruding in a radial direction of the rotor, and being installed within the rotary drum eccentrically with the same and being adapted to rotate reversely against the rotary drum.
A treatment system of granular substances with pollutants adhered according to a ninth aspect of the present invention, the treatment system carries out the fine granulation treatment of the granular substances with pollutants adhered such that the granular substances such as stones and gravels having large diameters, which have been mixed in the granular substances with pollutants adhered are classified from the slurry, which were discharged from a first stage fine granulation system, those separated granular substances having large diameters are poured into a latter stage fine granulation system and those granular substances having large diameters are accelerated by rotating the rotary drum and the rotor in a mutually reversed direction under a condition that the granular substances and granular substances having large diameters are mixed.
A method of carrying out treatment of granular substances with pollutants adhered according to a tenth aspect of the present invention is characterized in that the granular substances without containing pollutants and the granular substances having diameters inclusive of separated pollutants smaller than those of the granular substances without containing pollutants are separated out of the granular substances, which have been discharged from the fine granulation means according to the first aspect of the present invention, by a liquid cyclone.
A method of carrying out treatment of granular substances with pollutants adhered according to an eleventh aspect of the present invention is characterized in that the separation of the granular substances having large diameters without containing pollutants out of the granular substances, which were already subjected to the fine granulation treatment, is carried out by a negative pressure type liquid cyclone whose discharge pressure is raised by providing a nozzle consisting of an elastic material at a discharge port arranged at a lower portion of the liquid cyclone.
A method of carrying out treatment of granular substance with pollutants adhered according to a twelfth aspect of the present invention is characterized in that, after carrying out the fine granulation of the granular substances with pollutants adhered while adding water to the granular substances, the granular substances are stored in a liquid supply cistern of the liquid cyclone, a treatment water containing the granular substances are supplied to the liquid cyclone from a lower portion of the liquid supply cistern, and the granular substances are classified with respect to size of the same and also the treatment water containing the granular substances having small diameters discharged from an upper portion of the liquid cyclone is turned back to the liquid supply cistern.